Injection molding apparatus with integrated hot runner system

ABSTRACT

A hot runner injection molding apparatus comprising:
         a machine injection unit with a machine nozzle,   a first machine platen fixed to a machine base,   a second machine platen movable with respect to the first machine platen,   a hot runner manifold,   a plurality of hot runner nozzles,   a movable valve pin plate connected to plurality of valve pins,   at least one moving device for moving the movable plate with the valve pins ( 37 ) between at least two positions, whereupon the valve pins are displaced between at least two positions, wherein the first machine platen has a chamber within which the hot runner manifold, the movable valve pin plate and the moving device are arranged.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from German Patent Application No. 102011 116 053.5 filed Oct. 18, 2011, the contents of which areincorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to an injection molding apparatus for injectionmolding of small and miniature plastic parts.

BACKGROUND OF THE INVENTION

In such machines, molten material is fed from the screw barrel of anextruder via a manifold sprue bushing in an inlet melt channel of a hotrunner system and there in a plurality of output melt channelsfluidically connected to and downstream from the inlet melt channel.

Such an injection molding apparatus is known from the brochure “mannermicro-män 50” of Otto Männer GmbH, which is made available on thecompany website http://www.maenner-group.com and whose content is hereinincorporated by reference.

Known injection molding machines have a first machine platen, fixed tothe machine base and a second machine platen which is movable withrespect to the first machine platen. The first machine platen has anopening for the machine nozzle of the machine injection unit. A moldplate is mounted on the surface of the first machine platen opposite tothe second machine platen. A hot runner manifold with hot runner nozzlesis mounted on the surface of the mold plate. Moving means for theactuators of the hot runner nozzles are often mounted on the mold plateor on the machine platen.

This construction shows a large area of contact between the machineplaten and the mold plate and between the mold plate and the hot runnermanifold which assists heat conduction between these componentsresulting in energy loss in the hot runner system and thermal expansionof the machine platen. Further, the actuation means of valve pins arelocated behind the hot runner nozzles which results in a lower precisionin parallel actuation of the nozzles resulting from positioning of theactuators laterally next to the mold plate and hot runner system. Apositioning of the actuation means behind the nozzles also results inthe need of a long distance manifold sprue bushing and inlet meltchannel respectively.

It is therefore the object of the present invention to provide aninjection molding apparatus improving the specified drawbacks forproducing high quality small and miniature plastic parts.

An injection molding apparatus improving at least some of the specifieddrawbacks is described in the German patent application DE 10 2011 116053. The content of this application is also incorporated herein byreference.

The invention relates to an injection molding machine for producinginjection-molded parts having an injection station comprising aninjection nozzle arranged on a machine platen for discharging melt,wherein a molding tool is arranged on the machine platen which defines acavity corresponding to the injection-molded part, wherein the moldingtool comprises at least one first tool element which is stationaryrelative to the machine platen and one second tool element which isdisplaceable relative to the first tool element between an open and aclosed position by means of a closing device, and wherein the injectionnozzle is connected to at least one inlet of the cavity arranged on thefirst tool element by means of a hot runner system.

This type of injection molding machine is known from DE 10 2005 015 242A1. It comprises a molding tool having two tool elements which define acavity adjoining both tool elements for producing an injection-moldedpart. A first tool element is fixed on a first machine platen arrangedstationary to the injection nozzle and a second tool element is fixed ona second machine platen which is movable to open and close the moldingtool on the first machine platen toward and away from same. The firsttool element has an indentation on its rear side facing the injectionnozzle in which a hot runner system is arranged which connects theinjection nozzle to the inlets provided on the cavity for the melt. Thehot runner system is thermally insulated from the first tool element andthe machine platen. The hot runner system has the advantage that themelt within the hot runner system remains capable of flowing when theinjection-molded part solidifies such that virtually no residual sprueremains on the injection-molded parts after they're removed from themolding tool. This enables omitting the production step of separatingthe sprue from the injection-molded part. The hot runner system moreoverhas the advantage of reducing the plastic material used during theinjection molding because the melt remaining in the hot runner systemcan be used for injection molding at least one further injection-moldedpart. Yet the injection molding machine does have the disadvantage ofbeing of relatively large dimensions. Further disadvan-tageous is thatthe first, so-called hot molding tool is still relatively complex andexpensive.

SUMMARY OF THE INVENTION

To overcome these drawbacks a hot runner injection molding apparatus isproposed comprising a machine injection unit with a machine nozzle, afirst machine platen fixed to the machine base, a second machine platenwhich is movable with respect to the first machine platen, a hot runnermanifold having an inlet melt channel and a plurality of output meltchannels, a plurality of hot runner nozzles associated with the manifoldoutput melt channels, a movable valve pin plate connected to a pluralityof valve pins, wherein the valve pins are associated with the hot runnernozzles at least one moving means for moving the movable valve pin platebetween at least two positions, whereupon the valve pins are displacedbetween at least two positions relative to the valve seat of the hotrunner nozzle to control the amount of a molten material injected into amold cavity through the manifold and the hot runner nozzles. The firstmachine platen of the hot runner injection molding apparatus has achamber within which the hot runner manifold, the movable valve pinplate and the moving means for moving the movable plate are arranged.

It is therefore the object to provide an injection molding machine ofthe type cited at the outset which allows for compact dimensions.

This object is accomplished by the machine platen comprising an innercavity and at least one section of the hot runner system being arrangedwithin the inner cavity. Doing so advantageously enables the first toolelement to be of correspondingly compact design.

A hot runner system is to be understood as a body disposed between theinjection nozzle and the mold cavity which has at least one passage forthe melt to be introduced into the mold cavity, said passage thermallyinsulated from the molding tool and/or heatable such that the meltwithin the at least one passage remains capable of flowing, or moltenrespectively, upon the solidifying of the injection-molded part withinthe cavity.

Advantageous embodiments of the invention are set forth in thesubclaims.

In one advantageous embodiment of the invention, the hot runner systemcomprises a manifold having an inlet connected to the injection nozzleand a plurality of outlets each respectively connected to at least onecavity inlet, wherein the manifold is arranged in the inner cavity ofthe machine platen. The injection molding machine then allows theproducing of even complex and/or delicately formed injection-moldedparts. There is then also the further possibility of being able toproduce a plurality of injection-molded parts during just one singleinjection molding process.

In one advantageous embodiment of the invention, the hot runner systemcomprises at least one hot runner in which a valve comprising a closureelement which is displaceable relative to a valve seat is arranged, saidclosure element being in drive connection with at least one actuator,wherein the actuator is arranged in the inner cavity of the machineplaten. Doing so enables sprue patches to be virtually completedprevented, whereby the injection-molded parts can be manufactured ateven better quality and contouring accuracy.

However, other embodiments are also conceivable in which the at leastone hot runner can be designed as an open hot runner. The hot runnersystem can thereby be manufactured at even lower cost and have even morecompact dimensions. An open design to the hot runner can be advantageousparticularly in the case of a smaller hot runner cross section. An openhot runner can also be used for injection-molded parts having lowercontouring accuracy standards.

In another design of the invention, the valve seat is connected by meansof at least two channels to inlets of the cavity spaced apart from eachother. It is thereby even possible for these channels to be configuredas “cold” channels in which the melt contained therein solidifiestogether with the injection-molded part when the molding tool is cooledso that the injection-molded part can be removed. It is thus alsopossible for at least one hot runner and at least one cold channel to becombined in the inner cavity of the machine platen.

In one expedient embodiment of the invention, the hot runner systemcomprises a plurality of hot runners, in each of which at least onerespective valve is arranged, whereby each valve comprises a respectiveaxially displaceable, needle-shaped closure element, wherein the closureelements are arranged on a carrier plate which is displaceable in theaxial direction of the closure elements relative to the machine platenfor the synchronous actuating of the closure elements by means of the atleast one actuator, and wherein the carrier plate is disposed in theinner cavity of the machine platen. This enables a plurality of valvesto be actuated at the same time by the displacing of the carrier platewithin the machine platen.

It is advantageous for the actuator to be configured as a piston whichis preferably arranged in a section of the machine platen locatedbetween the carrier plate and the first tool element. Doing so enablesthe space located laterally next to the hot runner system between thecarrier plate and the first tool element of the molding tool to be usedto accommodate the piston. The piston can be pneumatically and/orhydraulically operated.

The manifold is expediently distanced from the machine platen by an airgap. Doing so allows the manifold to be easily thermally uncoupled fromthe machine platen and the first tool element arranged thereon.

In one preferential design of the invention, the manifold is detachablyconnectable to the machine platen, preferably such that a clampingsurface for the molding tool turned away and opposite the injectionnozzle comprises an opening into which the manifold can be inserted andthrough which the manifold can be removed. The manifold is then easilyaccessible, e.g. for performing service or maintenance on the manifold,after the molding tool has been removed.

The molding tool can be expediently fixed to the clamping surface bymeans of at least one clamping element, whereby the manifold isconnected to the first tool element at its rear side facing the clampingsurface. The manifold can then be removed from the machine platentogether with the stationary first tool element after the at least oneclamping element is loosened and be replaced by the appropriatereplacement part as needed.

In a further development of the invention, the injection molding machinehas, additionally to the injection station, at least one further stationand a transport device with at least one transport route connecting thestations on which the second tool element can be moved from one stationto another station, if applicable with an injection-molded part in thecavity. It is thereby possible to process the injection-molded parts atmultiple stations at the same time. The injection molding machine thusenables high productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

The following will draw on the figures in defining an embodiment of theinvention in greater detail. Shown are:

FIG. 1 a schematic plan view depiction of an injection molding machineaccording to the invention, and

FIG. 2 a partial cross section through a mold half of a molding toolarranged on a machine platen of an injection molding machine.

FIG. 3 shows a view of an inventive machine platen of a secondembodiment in cross section;

FIG. 4 shows a more schematic view of the inventive machine platen ofFIG. 3 in cross section with a machine injection unit.

DESCRIPTION OF THE DRAWINGS

Reference is made to FIG. 1 and FIG. 2 which are described in moredetail in the German patent application DE 10 2011 116 053.

FIG. 1 shows a micro injection molding apparatus 1 for manufacturingminiature molded parts 2 with a machine injection unit 3, a coolingstation 4, a part removal station 5 and a heating station 6. The machineinjection unit 3 has a machine nozzle 8 arranged at the machine platen 7for feeding melt.

A first mold half 10 is connected to the machine platen 7. The first andsecond mold halves 10, 11 are moveable in an open-close movement. FIG. 1shows an open position.

FIG. 1 shows a transposition system, with a closed transposition way 12connecting at least one of the stations 3, 4, 5, 6. The second mold half12 is movable along the transposition way 12, 13, 14, 15. Thereby themolded parts 2 can be handled at more than one station in parallel.

FIG. 2 shows a view of an inventive machine platen 7 of a firstembodiment in cross section. Via a hot runner system, the machine nozzle8 is connected to gates 28 of the cavity 9. The gates 28 are located ata first mold plate 10. The hot runner system is arranged in a chamber 29of the machine platen 7. The hot runner system comprises a manifold 30,which has a melt inlet 31 facing the machine nozzle 8. The manifold 30is connected via a hot runner 32 to a furcation 33. Further hot runnerchannels 34 lead from the furcation 33 to the gates 28. By means of aclearance the manifold 30 is spaced from the machine plate 7.

Within the manifold 30 heating elements 35 are arranged at the hotrunner 32 leading from the machine nozzle 8 to the furcation 33 and afurther heating element 36 is arranged for tempering the manifold 30.

Within each hot runner leading from the furcation 33 to a cavity 9, ahot runner nozzle 41 with a valve and a valve pin 37 are arranged. Thevalve pin 37 is axially movable and positionable against a valve seatclose to the cavity 9.

The valve pins 37 are arranged in parallel to each other and are fixedto a movable valve pin plate 38 with their ends opposite to the valveseat. The movable valve pin plate 38 is arranged within a chamber 29 inthe machine platen 7. With moving means 39 the movable valve pin plate38 is movable relative to the machine plate in an axially direction ofthe valve pins 37. In this way the valves of the nozzles 41 can beopened and closed synchronously.

The moving means are positioned lateral next to the inner chamber 29within the machine platen 7. The recesses for the moving means arelocated in an area of the machine platen 7 between the movable valve pinplate 38 and the mold plate 46.

FIG. 3 shows a view of an inventive machine platen 7 of a secondembodiment in cross section. The hot runner system is arranged in achamber 29 of the machine platen 7. The hot runner system comprises amanifold 30. By means of a clearance the manifold 30 is spaced from themachine plate 7.

At each hot runner leading from furcation 33 to a cavity 9, a hot runnernozzle 41 with a valve and a valve pin 37 are arranged. The valve pin 37is axially movable and thereby positionable against a valve seat closeto the cavity 9.

The valve pins 37 are arranged in parallel to each other and fixed to amovable valve pin plate 38 with their ends opposite to the valve seat.The movable valve pin plate 38 is arranged within a chamber 29 in themachine platen 7. With moving means 39 the movable valve pin plate 38 ismovable relative to the machine platen 7 in an axially direction of thevalve pins 37. In this way the valves of the nozzles 41 can be openedand closed synchronously.

The moving means 39 are positioned lateral next to the inner chamber 29within the machine platen 7. The recesses for the moving means arelocated in an area of the machine platen 7 between the movable valve pinplate 38 and the mold plate 46.

FIG. 4 shows a more schematic view of the inventive machine platen 7 ofFIG. 3 in cross section with a machine injection unit 3. The machineinjection unit 3 has a screw barrel 44 with feeds molten material to aninjection plunger 45 of a machine nozzle 8 which is positionable to themelt inlet 31 of the hot runner system of the injection moldingapparatus 1.

The hot runner system comprises a manifold 30, which is connected via ahot runner 32 and hot runner nozzles 41 to gates of mold cavities. Thehot runner system is arranged in a chamber 29 of the machine platen 7.By means of a clearance the manifold 30 is spaced from the machine plate7.

At each hot runner leading to a cavity, a hot runner nozzle 41 with avalve and a valve pin 37 are arranged. The valve pin 37 is axiallymovable and thereby positionable against a valve seat close to thecavity.

The valve pins 37 are arranged in parallel to each other and are fixedto a movable valve pin plate 38 with their ends opposite to the valveseat. The movable valve pin plate 38 is arranged within a chamber 29 inthe machine platen 7. The moving means 39 move the movable valve pinplate 38 relative to the machine platen 7 in an axially direction of thevalve pins 37. In this way the valves of the nozzles 41 can be openedand closed synchronously.

The moving means 39 are positioned lateral next to the inner chamber 29within the machine platen 7. The recesses for the moving means 39 arelocated in an area of the machine platen 7 between the movable valve pinplate 38 and the mold plate 46.

As can be recognized from FIG. 1, an injection molding machine 1 forproducing injection-molded parts 2 comprises an injection station 3, acooling station 4, an extraction station 5 and a heating station 6.

The injection station 3 has an injection nozzle 8 arranged on a machineplaten 7 for discharging melt. The melt can be conveyed to the injectionnozzle 8 by means of a known per se screw conveyor not shown in anygreater detail in the drawing.

A molding tool is arranged on the machine platen 7 which defines acavity 9 corresponding to the injection-molded part 2. The molding toolcomprises a stationary first tool element 10 connected to an injectionnozzle 8 and a displaceable second tool element 11. The tool elements10, 11 are respectively configured as mold halves. They can be movedtoward and away from each other and brought into an open position asdepicted in FIG. 1 as well as into a closed position. In the closedposition, the tool elements 10, 11 can be pressed together via clampingmeans not shown in the drawing in any greater detail.

It is also recognizable from FIG. 1 that the injection molding machine 1has a transport device which comprises at least one closed transportroute 12, 13, 14, 15 connecting the stations 3, 4, 5, 6. The second toolelement 11 can be moved along the transport route 12, 13, 14, 15 fromone station 3, 4, 5, 6 to another station 4, 5, 6, 3, with aninjection-molded part 2 in the cavity 9 as applicable. Theinjection-molded parts 2 can thereby be processed at multiple stationsat the same time.

The transporting of the second tool element 11 ensues by means ofrodless pneumatic cylinders 16, 17, 18, 19, whereby a first pneumaticcylinder 16 assumes the transport of second tool elements 11 arranged ona first slide rail 20, a second pneumatic cylinder 17 assumes thetransport of second tool elements 11 arranged on a second slide rail 21,a third pneumatic cylinder 18 assumes the transport of second toolelements 11 arranged on the third slide rail 22 and a fourth pneumaticcylinder 19 assumes the transport of second tool elements 11 arranged ona fourth slide rail 23. Slide rails 20, 21, 22, 23 arranged adjacentlynext to one another are respectively connected together by means ofrotary drives 24, 25, 26, 27.

It is recognizable from FIG. 2 that the injection nozzle 8 is connectedby means of a hot runner system to inlets 28 of the cavity 9 arranged onthe first tool element 10. The hot runner system is arranged in an innercavity 29 of the machine platen 7. The hot runner system comprises amanifold 30 having an inlet 31 facing the injection nozzle 8 which isconnected to a branch point 33 by means of a hot runner 32. Further hotrunners 34 lead from the branch point 33 to the individual inlets 28. Aclearance distances the manifold from the machine platen 7.

Heating elements 35 are arranged in the interior of the manifold 30which keep the manifold 30 at a temperature at which the melt thereinremains molten or capable of flowing respectively. The heating elements35 can be configured as electrical heat conductors. A further heatingelement 36 is provided on the hot runner 32 leading from the injectionnozzle 8 to the branch point 33 for thermoregulating the manifold 30.

A respective valve comprising a needle-shaped closure element 37 whichis axially displaceable and can be positioned against a valve seat inclose proximity to the cavity 9 is provided in each of the individualhot runners leading from the branch point 33 to the cavity 9.

The closure elements 37 run parallel to one another and are fixed to acarrier plate 38 arranged within the inner cavity of the machine platen7 by their end remote of the valve seat. The carrier plate 38 isdisplaceable in the axial direction of the closure elements 37 relativeto the machine platen 7 by means of pistons 39. The valves can therebybe opened and closed synchronously.

The pistons 39 are displaceable within bores positioned laterally nextto the inner cavity 29 in the machine platen 7. The bores are arrangedin a section of the machine platen 7 located between the carrier plate38 and the first tool element 10.

The manifold 30 is detachably connected to the first tool element 10 bymeans of screws 40 and can be removed from the machine platen 7 togetherwith same.

What is claimed is:
 1. A hot runner injection molding apparatuscomprising: a machine injection unit including a machine nozzle; a firstmachine platen, fixed to a machine base, a second machine platen whichis movable with respect to the first machine platen; a hot runnermanifold having an inlet melt channel and a plurality of output meltchannels a plurality of hot runner nozzles associated with the manifoldoutput melt channels; a movable closure elements carrier plate or valvepin plate connected to a plurality of valve pins or to a plurality ofclosure elements, wherein the valve pins or closure elements areassociated with the hot runner nozzles; at least one moving actuatordevice that moves the closure elements carrier plate or the plate withthe valve pins between at least two positions, whereupon the valve pinsare displaced between the at least two positions relative to a valveseat of the hot runner nozzle to control the amount of a molten materialinjected into a mold cavity through the manifold and the hot runnernozzles; wherein the first machine platen being adjacent the machinenozzle of the injection unit and wherein the first machine platenincludes a multi-portion chamber or an inner cavity within which the hotrunner manifold, the movable carrier plate or valve pin plate and theactuator device are at least partially arranged.
 2. The injectionmolding machine according to claim 1 wherein the manifold is arranged ina first portion of the chamber of the stationary machine platen.
 3. Theinjection molding machine according to claim 1 wherein the actuatordevice is arranged in a second portion of the inner cavity or thechamber of the stationary machine platen.
 4. The injection moldingmachine according to claim 1 the carrier plate being disposed in aportion of the inner cavity or the chamber of the stationary machineplaten.
 5. The injection molding machine according to claim 3 whereinthe actuator comprises a piston which is arranged in a section of thefirst machine platen that includes a portion of the chamber locatedbetween the carrier plate and a first tool element.
 6. The injectionmolding machine according to claim 1 wherein the manifold is detachablyconnectable to the machine platen and a clamping surface for the moldingtool that is turned away from and opposite the injection nozzle has anaperture into which the manifold can be inserted and through which themanifold can be removed.
 7. The injection molding machine according toclaim 1 wherein a molding tool is fixed to a clamping surface of atleast one clamping element and the manifold is connected to a first toolelement at a rear side of the manifold facing the clamping surface. 8.The injection molding machine according to claim 1 wherein the injectionmolding apparatus comprises at least one further station.
 9. Theinjection molding machine according to claim 1 further comprising atransport device having at least one transport route connecting thestations on which a second tool element can be moved from one station toanother station with an injection-molded part disposed in the cavity.